Totipotent stem cells, such as embryonic stem (ES) cells, can differentiate in vivo into all cell lineages, and, when induced in vitro, differentiate into most cell types. ES cells are derived from early mammalian embryos. Due to their totipotency, they are believed to hold a great promise for treating degenerative or inherited diseases. However, ethical and logistical considerations have hampered the use of human ES cells in research and therapy. Totipotent or pluripotent stem cells of non-embryonic origins (e.g., from tissues of adult or young animals) would circumvent this obstacle. Although some stem cells have been obtained from such non-embryonic origins, some of these cells have limited developmental potentials. Also, logistically, these cells are difficult to obtain and amounts of the cells are too limited to meet meaningful clinical or research uses. Furthermore, some of the cells can develop into teratoma in vivo and therefore are not desired for in vivo uses. There is a need for non-embryonic totipotent or pluripotent stem cells that are safer and easy to obtain, and have an abundant source.